Device for testing materials



Jan 6,l v1931- G. s. v. HEYDEKAMPF 1,787,525

DEVICE FOR TESTING MATERIALS Filed May 3. 1929 2 SheeiS-Sheet 1 Figi Fig2 zur li n Mii Inl/@pfors @www 1f f ffm/f Jan 6, 1931. s. v. HEYDEKAMPF 1,737,525

DEVICE FOR TESTING MATERIALS Filed May 3, 1929 2 Sheets-Sheet 2 Patented `lam. 6, 1,931'

, `Unirse. lsra'rss PATENT i OFFICE GERD srrnnnn v. HEYDEKAMrF, oF BanNsvvIcK, GERMANY, VAssreNoR fro OTTO Ferri., or BRUNSWICK, GERMANY p Drivicnron 'rnsTrNG MarrnRrALs x ln the'cu'stomary devices yor producing oscillations of flexurebased upon the number ofnatural oscillations, the test-piece (flat spring) is at one end secured and provided at the other end with a mass, the dimensions of which are small in proportion to the length of the ytf-zst-piece. For this reason only a single force `is mainly transferred` fromr the test-piece to the mass, -which is necessary for i@ theparallel displacement of thefmass, Whilst .the` torsional moment, simultaneously transferred, is of a negligible quantity. In these arrangements the moment of flexure Atrans-V ferred into the test-piece varies over the Whole length of the latter. it the end of the test-piece, where it is secured, the moment of 'lexureV is largest, decreasing linearly from that point to the mass Whereits value is Zero.

ln contra-distinction thereto the present invention purposes to produce device, in which the strain of the test-piece by `oscillations of fleXure is distributed as uniformly as possible overthe entire length4 of the testpiece. To this end the oscillatory-,mass engaging theffree end of the test-piecel has been` so designed in accordance with the invention,

that it is adapted t-o Aaccumulatefenergy not only through the medium; ofptheidisplace ments of the centre 'of gravity of the mass, but also through the mediumfof torsions. ln accordance with the invention the amount of force required for the torsional movement is advantageously enhancedrso as toattain such considerable values `owing to the special L. design of the oscillatory mass, that the force of the torsional. movement is'appr-oXimatel Y` of the same value as the forceof translatory motion. For this purpose the mass has `not been given the customary shape of a square block, but-has been designed as oscillatory body, possessinge.` gthe form of a double T (I) in which the masses are removed`Y from their axis of rotationd as far as possible.

Owing to this additional torsional oscilla ltion the strain of the test-piece is composed of a linearlyincreasing moment and a second but invariable moment. rEherefore, the nev.' device, in contra-distinction to those cus- A tomarily used so far, embodies-the advan-- tage, that the moment is .variable along the sfso,27f.s,"ami` in eeimnynay 21, 192s.

test-piecev toa lesserdegree and that in con-y ljunctiony with a suitable design of the new device the strain may even be distributed uni* forinly `over the entire length of the testpiece. y I c ln the drawing the invention has been represented by Way of example, y

Fig.. 1' showing schematically the customary device in use so far, together with a graphic representation of forces appertaining thereto'. f

- Fig. 2 represents the neiv form of construction schematically togetherv with a graphic representation of'f-orces. f f

Fig.4 3 illustrates a preferred form vof construction of the neu7 device schematically together,- With a graphic representation of forces. f y

Fig.-lis a front-view of the new device as example of performance. n f

Fig, 5 is a'lateral sectional view along the line -i-'of Fig. ll. p

Fig. 6 is a vertical sectional along the line 6 6 of Fig. 5.

Fig. 7 illustrates electric actuation.

ln kthe'test-arrangement hitherto used, as shown in Fig. 1,@ represents the test-piece to the connections for the `be tested and which is firmly securedat 6, carrying at itsfree end the mass m. If the acceleratingforce presentingitself upon ose cillating themass m is called P, then the momentof flexurelE=P- l. The strain show-y ing itself in the `test-piece in conjunction here- With is greatestat the'point Wherethe test piece is secured at b, viz. P. l, gradually decreasing in the direction of the free end of the test-piece down to zero. rlhis course of the moment of fleXure has been represented graphically vin the right half of Fig. l in the form of atriangle.

, In the new device is accordance With Fig.

2 the mass m has been given the shape of a double 'l' (l), With the result that, similar to )ally-Wheel, the kmass-parts m', m are situated at the greatest possible distance from thecentre of gravity o. With the oscillation of the test-piece a an absorption principally takes place, therefore, through the torsional acceleration of the mass about rzoL - the axis d, whilstthe lateral acceleration of the centre of gravity @and the absorption of force eifected thereby` is of avsmalller value. As a result thereof thelateral acceleration vwill yield a moment of flexure M1 which,'as in the design according to Fig. 1, is variable over the entire length of the test-piece. In addition thereto must be considered a moment of lexure M2 as a result of the torsional acceleration, which'moment of iiexure remains uniform over the ent-ire length of the test-piece, as elucidated by the graphic rep-r resentation of forces on the right of Fig. 2. The' resulting moments may likewise bef-deduced from thegraphic representation of forces beside Fig. 2 which shows that, compared with the design as per Fig. l, the strain of the test-piece is essentially' more uniform.'

A. perfect uniformity of strain may be at-V tained, if the moment Ml resulting from the lateral displacement iscaused to be trans--` ferred by means of special auxiliarysprings which are shown in Fig. 5 and described in detail later on.' Therepremains the proper dimensioningof the auxiliary springs'for the test-piece and then the moment of flexure M2 will be uniformly Vdistributed over the entire length of the'test-piece as shown-'schematically in the left half of/Fig. '3. -In such a design the rotary movement ofthe oscillatory j mass takesv placeroundL nthe pointcl in Fig.- 3.

d is 'placed at lhalf the height of the testpiece,`because the flexure of the testlpiece corresponds to a circular track. The'geometric centre of the oscillatorymass is suitably placed at d; in conjunction herewith it necessary to cause m in Fig.: 8 to be larger than m, so as to ensure the centre vof gravity c remaining, as before, on a level with the end of the spring, i. e. a distance above the centre of rotation d. Y n Y vThis tlevice'renclers'it possible to utilize a rspecially advantageous .actuation of the' cfscillatory 'arrangement'V by means of electromagnets. For the purpose vof ensuring ,that

inf this arrangement the lower half of the oscillatory mass may' swing past the test-piece,

the-mass requires to be disposedlaterally to Y thelatter." For the purpose of obviating in 'connection herewithany disturbing unilateral forces, it is advisable to Vselect a symmetrical design, in which eitherthe oscillatory mass is divided up in two halves, or vice versa, a test-piece each may be arranged on either side of the oscillatory mass.

Figs. 4-6 represent-sra practical yformof construction of the last mentioned design of the object of the invention based upon the principle schematicallyv represented in Fig. 3.'

In .this case the device consists of -a framelike structure, `formed by twoV lateral uprights v1, Qiand the'two horizontal stays 3, l and provided with two feet 5, 6 consisting of angle-- 1ron. In the'lower part of thisstructure two horizontalrbridges 7, 8 ofTeiron havebeen attached which serve Vas a rest for the clamping device. These clamping devices are each formed by one of the angle-irons 9, 10 attached to the bridge 7, 8 and a clamping plate 12 to be In each ofthe two clamping-devices a testl .piece f1 and f2 in most cases consisting a fiat spring, of which the upper end is engaged "by'thfe oscillatory'mass 15, has been secured.

This oscillatory'mass consists, if seen in front- .view (Figa) of a T-shaped body, carrying in front andbehind onetransverse arm 16, 171 eachjwiththe result-that,fseen laterally, it re-V sembles a cross as per Figli). The transverse arms 1.6,A 17 are each provided witha vertical longitudinal slot, in whichy the upper ends of Vthe vtwo utest-pieces f1, f2 are made to engage and where theyV are secured` or clamped by means of screws 18. Y i

The oscillatory mass may now, by subjecting thesprings f1, 'f2 to a bending strain perform a displacement to the right and'to theV leftonthe one hand and on the other hand it will be able to .describe a rotary movement*round-its'axis el, as has'been indicated in Fig. 4t byfmeans of dot-ted lines.

VIn view of the fact, that in this' arrangementfthe axis of rotation is placed at half the height of the spring,the oscillatory mass w1ll describe an almost purely rotary motion round the axis d Vduring the oscillation, a

formiof motion, which not only guarantees a. uniform strain over'the whole length *ofA Vsecured at the top like the test-piece f1, f2,

but held bymeans of narrowledges 19 (Fig. 5) bythe transverse arms 16, 17 ofthe oscillatory mass. They are so dimeusioned, 'that they are subject to an inconsiderable strain only. 'Ihey may, therefore, remain permanently inthe device without risk of breakage, whilst the`test-piece f1', f2 have to be exchanged each time. Y

The auxiliary Vsprings. should, compared with the test-pieces, be so dimensioned, that vduring bending orfiiexure they just take up or absorb the moment M3. (Fig. Q). If they are too weak, the test-pieces have to take up part of the moment M1, which is increased in a downward direction, and they will break below. If, however, `the-auxilit.ry springs are too strong, they will take up or absorb part of the moment M2' with the result, that the .test-pieces ywill break at the top. The position lof the fracture will, therefore, al-

fastened thereto by means of screws ways furnish means for ascertaining as tok ends 22,23 of the oscillatory mass and attached to the' rigid `frame of the device by means of screws 24. These pairs ot electromagnets are now selectively-so excited by the coils 25, that alwaystwo magnets placed dianietrically to each other are made to act, endeavouring to attract the oscillatory minis so as to assume the one or the other oblique position. All four electro-magnetsare placed fairly close to the vertical intermediate planevwith the result that the line of connection'y of two co-ordinated magnets is. practically vertical. This ensures a specially advantageous and uniform actuation, be-l cause any inconsiderable horizontal displacements which may show themselves., will not cause any essential changes in the air-gap between the oscillatory mass and-the electromagnets.

The control of the electro-magnets isV et- 'f'ected in accordance with the connections or wiring-scheme shown in Fig. 7 in dependence Aot' the movement of the oscillatory mass by the latter itself through the medium ci a small converter' 30, which is supported by a U-shaped carrier 30 attached to a traverse 31 of the structure. This converter 30 is of the so-called friction-switch type i. e. the transmissionof motion is effected by friction with another moveable part. To this end the oscillatory mass is made to carry an arc 32 curved round the aXis of rotation cl; this are establishes contact with the rearward end of the switch lever and tends to take the switch-lever with it so far in one or the other direction, until its further progress is hindered by the stops at the contacts 33, 34, thereby closing the current for the one vor the other pair of magnets. Together with the reversal of motion of the. oscillatory mass in its limiting position, the reversal of control is eected simultaneously each time.

The connections or wiring scheme is illustrated in Fig. 7. The supplyof current is taken from the feeder 40, 4l via the fuse 42 and the main-switch 43 attached to a potentiometer 44, to one end of which the pair of magnets 20, 20V has been connected and to the other end the pair of magnets 2l, 2l', whilst the centre of the potentiometer 44 is connected with the point of rotation of the switch lever 30 via al regulable resistance 45. The switch lever 30 which,.as will be seen from Fig. 6, is moved to and'fro by theV oscillatory mass, alternately acts thereby together with the two contacts 33, 34,y which each appertain to one of the two pairs of magnets. Parallel to each point of interruption a condenser 146i, 47' has been .positioned in orderlto reduceftliefforniation of sparks.

The sameeiect, moreover, is exercised .by thetwo halves of the po-tentiometer 44,'lwhich are connected in parallel to the magnets. To one part of. the series -resistance 45 an electric `counting device 48, ofa kind knownin itself, has been connected in parallel. This counting device which'is actuated by thefcurrent impulses after the style ot asynchroi nous motor renders it possible .to ascertain from its number of revolutionsv the number or 4oscillations performed by the oscillatoryf ina-ss until the fracture of the test-piece; V

For the purpose of attaining an automatic interruption 'of theA actuation in coniunction :with-such fracture, the two sides of the oscillatory mass have beenequipped with an auxiliaryrcontact `v50,` lfeach. It now.=the

amplitude grows beyond a certain limit owing vto the fracture of a test-piec'e'or for any other 1 reasons, the oscillatory mass will strike againstvr one oftheauxiliary contacts 50, 51, thereby closing the -current of the releasingcoil -52, causing the main-switchl 43 to `be actuated and thus interrupting theworking of` the device. lThegresistance serves for limiting-theauxiliary current.

T claim:

l. Device` `forA testing -*co*nstructio'nal niate- 1 rial by oscillations of lexiire of resilient-testpieces which comprises means for securing a test-piece at one end to a fixed support, and an oscillatory mass carried at the other end of the test-piece and so arranged with respect thereto as to act as a torsional oscillatory mass in such a manner that the strain ofv the test-piece throughthe torsion of the oscillatory mass will equal at least that exercised by the displacement of the oscillatory mass.

2. vDevice in accorda-nce with claimv l wherein the oscillatory mass and test-piece are disposed. symmetrically on either side of the intermediate plane of oscillations in such a manner, that their paths of oscillations overlap each other.

3.oDevice sin' accordance with claim 2 wherein the oscillatory mass is supported at each side by a test-piece.

4. Device in accordance with claim l wherein two test-pieces are mounted to stand upright and support thevoscillatory mass.

5. Device in accordance with claim l' wherein the oscillatory massis T-shaped.

6. Device in accordance Vwith claim l wherein the oscillatory mass' projects atits ends longitudinally beyond the ends of the test-piece.

7. Device in accordance with claim 1l wherein electro-magnetic means is provided comprising electro-magnets disposed on opposite sidesof the ends of the oscillatory mass.

8. Device in accordancev with claim 1,

2ll Y Y- 1,787,6255Y characterized-thereby, thatpthe test-piece is Y Y coupledfto theoscillatory 'massso far above the center'of said mass,.that itsgtorsion takes placeroundan: aXis which is situated :at about -5 half the-heightfof the test-piece. e,

.19. Device in acordance with claim Yl WhereinauXiliary springs-are provided'inladdition tothey test-pieces proper which are held loosely engaged attheir upper endswith 10 the oscillatory mass, so that .duringtheoscilv lation they can take np or absorb'primarilyY oneforce only. Y Y 10. Device inA vaccordance with claim lVV wherein `auxiliary springs are `provided for L; lleXure by movements ofthe -Inass, which auxiliarysprings are sodimensionedinproportion to the .test-pieces, that' they take up y or absorb the Vmoment originated'bytheidis placement/of the centre of gravity, so that l 2O the-test-pieces Will have a inolnentinvariable along their length, produced bythe torsion of the oscillatory mass.

"11. lDevice y in accordance With claim l wherein :electro-magnets .are employed to V'actuate the massand wherein current to the magnets is governed by a friction-switch which effects the connection inV accordance With the direction of velocity oi the oscilla-- tory mass. 'Y Y Y Y Y Y 30 Y In testimony-whereof yI affix my signature.

vGERD sTIELER WHEYDEKAMPF. 

